In the field of printable electronics there are electrochemical devices with many different fields of application, such as electrochromic displays and electrochemical transistors. The electrochemical devices involve electrochemically active material and electrolyte, and are typically based on layered structures having lateral or vertical architectures which allow for manufacturing by means of conventional printing techniques. The various fields of application of these types of electrochemical devices relates to e.g. optical, electrical, and/or volumetric properties and effects, wherein the device and its application is controllable by altering the electrochemical state of the device. In other words, the electrochemical devices, and the effects, are controllable by electrochemical switching which may be achieved, for example, by applying a potential difference between the electrochemically active material and the electrolyte. Also, the effects of a device may be controlled in order to define various electrochemical devices with various operations and applications. For example, the above described electrochemical devices find application in the field of printed electronics ranging from sensors and single pixel devices to logic circuits and large active matrix addressed display systems.
U.S. Pat. No. 6,642,069 describes an electrochemical pixel device which includes two components each comprising an electrochemical device. The first component, an electrochemical transistor, is in the electrochemical pixel device arranged to control the second component, an electrochromic display element. The configuration and application of the device gives rise to an electrochemical reaction in the electrochemical transistor, wherein the redox state of the transistor controls the progress of an electrochemical coloring or de-coloring of the electrochromic display element. In more detail, by applying a potential difference between a gate electrode and the transistor channel, the electrochemical redox state of a transistor channel of the transistor is changed due to a controlled electrochemical reaction. The change of redox state of the transistor channel further changes the conductivity of the transistor channel, and by controlling the conductivity of the transistor channel, the redox state and the progress of an electrochemical reaction in the electrochromic pixel element is controllable, which allow for coloring or de-coloring operation of the pixel. Hence, by controlling the electrochemical switching of the transistor channel, the electrochemical switching of the pixel element is controlled and achieved so as to switch it between a colored and non-colored state. General properties, such as switch time and delay time, of the electrochemical reaction in the transistor channel and in the pixel element determine the performance of the device and the finished product. As described, the electrochemical switching of the electrochemical device entails electrochemical reactions, wherein the electrochemical reactions comprise transportation of ionic charges. The above described properties of the electrochemical switching give rise to that the typical switching characteristics of an electrochemical device is disadvantageous in terms of switch time and that the electrochemical device is susceptible to discoloration related to the electrochemical reactions. Moreover, the electrochemical devices may show switching characteristics which are dependent on if the device is switched from a low reacted state to a high reacted state, and vice versa, which further burdens the performance of the device.